Is a fever and a white blood cell (WBC) count of 18,600 considered normal in a pregnant woman in her third trimester?

Fever and Elevated WBC Count in Third Trimester Pregnancy

A white blood cell (WBC) count of 18,600 with fever in a third-trimester pregnant woman is abnormal and requires urgent evaluation, as it likely indicates infection or inflammation that could impact maternal and fetal outcomes.

Normal WBC Values in Pregnancy

Pregnancy naturally causes physiological leukocytosis, but even during the third trimester, there are limits to what's considered normal:

• Normal WBC range in third trimester: 5.7-15.0 × 10^9/L 1
• Normal neutrophil range: 3.7-11.6 × 10^9/L 1
• Progressive increase in D-dimer levels is also normal during pregnancy (third trimester: 0.16-1.3 μg/mL) 2

Significance of WBC Count of 18,600 with Fever

A WBC count of 18,600 exceeds the upper reference limit for pregnancy and, when combined with fever, strongly suggests an infectious process requiring immediate evaluation. This combination of findings warrants prompt medical attention because:

1. Elevated WBC counts >15,000 during pregnancy with fever are associated with:

   • Increased risk of maternal morbidity
   • Higher rates of ICU admission when severe 3
   • Potential for respiratory complications, especially in the context of infections 3

2. Fever itself is concerning in pregnancy and can be associated with:

   • Intrauterine infections
   • Respiratory infections (particularly concerning in third trimester)
   • Urinary tract infections
   • Chorioamnionitis

Diagnostic Approach

The following investigations should be performed immediately:

• Complete blood count with differential to assess neutrophil predominance
• Blood cultures
• Urinalysis and urine culture
• Chest X-ray (with appropriate abdominal shielding)
• Assessment of fetal well-being (NST, BPP)
• C-reactive protein level (elevated CRP with high WBC correlates with more severe disease) 3

Potential Diagnoses to Consider

1. Respiratory infections - Particularly concerning as they can progress to pneumonia/ARDS in pregnant women 3
2. Urinary tract infections/pyelonephritis - Common in pregnancy and can cause significant leukocytosis
3. Chorioamnionitis - Infection of amniotic fluid and membranes
4. Appendicitis - Can present atypically in pregnancy
5. COVID-19 or influenza - Can cause severe disease in pregnant women 4

Management Considerations

• Empiric antibiotic therapy should be initiated promptly after cultures are obtained
• Close monitoring of maternal vital signs and fetal status
• Delivery considerations may be necessary if infection threatens maternal or fetal well-being
• ICU preparation may be needed, as patients with significantly elevated WBC and CRP levels have higher rates of ICU admission 3

Important Caveats

• While pregnancy-induced leukocytosis exists, WBC counts >20,000 without infection are rare 5
• Fever is not a normal finding in pregnancy and always warrants investigation
• The combination of fever and marked leukocytosis requires urgent evaluation and treatment
• Delaying treatment of serious infections in pregnancy can lead to adverse maternal and fetal outcomes

Remember that while physiological changes in pregnancy can alter laboratory values, a WBC count of 18,600 with fever exceeds normal physiological changes and requires prompt medical attention to identify and treat the underlying cause.